It is a technology that providecomputation, software, data access, and storageservices that do not require end-user knowledgeof the physical location and configuration of thesystem that delivers the services. It deliver applications via the internet, which areaccessed from web browsers and desktop andmobile apps, while the business software and dataare stored on servers at a remote location.
It is a delivery model for IT, the servicesbased on Internet protocols, and ittypically involves provisioning of dynamicallyscalable and often virtualized resources. Itis a by-product and consequence of theease-of-access to remote computing sitesprovided by the Internet.
The underlying concept of cloud computing datesback to the 1960s, when John McCarthy opinedthat "computation may someday be organised as apublic utility.“ Almost all the modern-day characteristics ofcloud computing, the comparison to the electricityindustry and the use of public, private, andcommunity forms, were thoroughly explored inDouglas Parkhills 1966 book, “The Challenge ofthe Computer Utility”
The actual term "cloud" borrows fromtelephony, who until the 1990s offered primarilydedicated point-to-point data circuits, beganoffering Virtual Private Network (VPN) serviceswith comparable quality of service but at a muchlower cost. In early 2008, Eucalyptus became the first open-source, AWS API-compatible platform fordeploying private clouds. In early 2008,OpenNebula, enhanced in the RESERVOIR EuropeanCommission-funded project, became the firstopen-source software for deploying private andhybrid clouds, and for the federation of clouds.
Empowerment of end-users of computing resourcesby putting the provisioning of those resources intheir own control, as opposed to the control of acentralized IT service (for example) Agility improves with users ability to re-provisiontechnological infrastructure resources. Application programming interface (API)accessibility to software that enables machines tointeract with cloud software in the same way theuser interface facilitates interaction betweenhumans and computers.. Cost is claimed to be reduced and in a public clouddelivery model capital expenditure is converted tooperational expenditure.
Device and location independence enable users toaccess systems using a web browser regardless oftheir location or what device they are using(e.g., PC, mobile phone). As infrastructure is off-site(typically provided by a third-party) and accessed viathe Internet, users can connect from anywhere. Reliability is improved if multiple redundant sites areused, which makes well-designed cloud computingsuitable for business continuity and disaster recovery. Scalability and Elasticity via dynamic provisioning ofresources on a fine-grained, self-service basis nearreal-time, without users having to engineer for peakloads.
• Service Provider makes Resources• May be free or pay-per-usage modelPublic• Managed internally or by 3rd party• Cost spread over few usersCommunity• Composition of 2 or more clouds• Data -one deployment system to anotherHybrid• Operated solely for single organization• User has to “buy, build and manage”Private
Privacy: The model poses privacy concernsbecause the service provider at any point intime, may access the data that is on thecloud. They could accidentally ordeliberately alter or even delete some info. Compliance: In order to obtain compliancewith regulations includingFISMA, HIPAA, and SOX, users may haveto adopt community or hybrid deploymentmodes that are typically more expensiveand may offer restricted benefits.Issues
Legal: Certain legal issues arise; trademarkinfringement, security concerns to the sharing ofpropriety data resources. Security: Concerns are being voiced about thesecurity issues introduced through adoption ofthis new model.Solutions to cloud security issues vary, fromcryptography, particularly public keyinfrastructure, use of multiple cloudproviders, standardisation of APIs, and improvingvirtual machine and legal support.
Sustainability: Although cloud computing is oftenassumed to be a form of "green computing", thereis yet no published study to substantiate thisassumption. Energy efficiency can result fromenergy-aware scheduling and server consolidation. Abuse: Crackers posing as legitimate customerscan purchase the services of cloud computing fornefarious purposes. This includes passwordcracking and launching attacks using thepurchased services.